Catalysis of Organic..

Canning, Gamman, Jackson and Urquart 69100473 K 573 K 673 K80Selectivity (%)6040200Pd-KOH Ni-KOH Pd-KOH Ni-CsOH Pd-CsOH Ni-CsOHPd-CsOH Ni-CsOH Ni-KOH Pd-KOH Ni-KOHMIBK MIBC Isophorone OthersFigure 2. Selectivity after 24 h on-line.the Pd-CsOH/silica catalyst had the highest activity and also maintained its highselectivity. After 24 h on-stream at 473 K only two products (MIBK and methylisobutyl carbinol (MIBC, 4-methyl pentan-2-ol)) were detected for all thecatalysts except Pd-CsOH/silica, which produced only MIBK. There were nosecondary aldol by-products, the hydrogenation of MIBK to MIBC was the soleroute to an undesired product. As expected palladium was poorer athydrogenating the carbonyl group compared to nickel and hence gave the higherselectivity. The product yields for the four catalysts at 673 K are shown inFigure 4.The range of species produced reflects the overall mechanistic schemeshown in Figure 1. The detail however gives insights into the differentprocesses and the effectiveness of the catalyst components in catalysing aspecific transformation.